Electromagnetic transducer mounting



1957 I c. M. TARIS ,8 05

ELECTROMAGNETIC TRANSDUCER MOUNTING Filed July 30, 195; 2 sheets-sheet 1INVENTOR C. M. TA R/S A TTORNEV Aug. 13, 1957 c. M. was 2,802,905

ELECTROMAGNETIC TRANSDUCER MOUNTING Filed July 30, 1953 2 Sheets-Sheet 2nvvaw TOR C. M. TA RIS A r TORNEI/ F: m 1 3%? :z.

lUited States ELECTROMAGNETIC TRANSDUCER MOUNTING Charles M. Taris,Cranford, N. 3., assignor to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New York Application July 30, 1953,Serial No. 371,388

3 Claims. (Cl. 179-1001) This invention relates to mountings fortransducers and particularly to mountings for electromagnetictransducers.

It is an object of this invention to provide a mounting which willfacilitate the control and adjustment of the pressure of the transduceron the record, medium, the tangency of the transducer recording andreproducing element with respect to the record medium, and the gapbetween the transducer and the record medium if outof-contact operationis desired.

A feature of the invention resides in supporting the transducer by meansof two adjustable rod members which are disposed to ride on the surfaceof the record medium, one of said rod members preceding therecording-reproducing element in its travel around the record medium,the other following said element.

The nature of the invention and its distinguishing features andadvantages will be best understood from the following detaileddescription and the accompanying drawings in which:

Fig. l is a view in perspective of a preferred embodiment of theinvention;

Fig. 2 is a fragmentary view in front elevation of the transducermounting and carriage mechanism shown in Fig. 1;

Fig. 3 is a sectional view taken on the line 3-3 of Pig. 2; and

Fig. 4 is a partially sectioned view of the transducer mounting shown inFigs. 1, 2 and 3.

Referring now to the accompanying drawings, 2 is a record drum which maybe made of a material such as aluminum. It is assembled on a shaft 4 onbearings contained in the drum and is driven from the shaft by means ofa constant torque clutch, the collar 6 of which is fixedly attached tothe shaft 4 and the plate 8 of which comprises a compliant member 10which is in constant frictional engagement with the drum. The shaft 4may be driven by means of the motor 12, the pulley 14 and the belt 16.Rotation of the drum is prevented by means of a pawl 18 which whenreleased by the solenoid 20, falls into a notch 22 in the drum.

On the peripheral face of drum 2 is mounted, under radial tension, aflexible, radially extensible magnetizable record band 24. The elasticrecord band 24 may comprise a homogenenous mixture of rubber and afinely divided ferromagnetic material. It may be molded in the form of aseparable tube which can be stretched over the drum 2, or it may bemolded directly on the drum.

The lead screw 26 is actuated by shaft 4 through gears 28, 30 and 32 andis engaged by the half nut 34, attached to the transducer carriage 36,to move the electromagnetic transducer 38 across the record member 24during both recording and reproducing operations.

The transducer carriage 36 is supported on and guided by the rods 40 and42 which are disposed on the bail 44. The transducer 38 is attached tothe carriage 36 by means of the support arm 46 and is moved toward therecord band 24 by means of the spring 48 when the 2,002,% Patented Aug.13, 1957 bail 44 is released by the solenoid 50. When this occurs thehalf nut 34 engages the lead screw 26 and the transducer is advancedalong the record band. When the solenoid 50 is energized the bail ismoved away from the record band, the half nut is withdrawn from the leadscrew, the transducer is lifted from the record band, and the transducercarriage is returned to its initial position by means of the spring 52.

The transducer 38 is a unitary structure comprising a core of magneticmaterial 54 formed to provide con verging pole tips 56 and 58 and arecording-reproducing gap 60, recording-reproducing coils (not shown)wound on the core and a mounting block member 62, preferably ofnon-magnetic material, within which the core and coil members arefixedly disposed and secured. The mounting block member 62 is pivotallyconnected to the sup port arm 46 by means of the pin 63, and allowed topivot freely within the range controlled by the stop pin 64 and the slot66.

- The tangential relationship between the transducer core at gap 60 andthe peripheral surface of the record band is controlled by means of rodmember 70 which precedes gap 60 in its relative travel around the recordband and rod member 68 which follows gap 60 in its travel. In thepreferred embodiment of the invention each of these rod memberscomprises a rounded-off portion 72, which extends beyond the mountingmember, rides on the record band and is made of a material such assapphire, and a screw portion 74 which is bonded to the rounded-offportion and is secured to the mounting member 62 by means of a lock nut76. The rod mcmbers 68 and 70 may be disposed in the mounting member 62in such manner as to be parallel, and normal to the pivot pin 63. Byturning one or both of these rod members in the mounting block, tangencyof the transducer gap with respect to the record band, and the desiredspacing between the pole tips and the record band can be establishedsimultaneously. After the desired conditions have been established, bymeans of rod members 68 and 70, lock nut 77 may be used to regulate thefreedom of movement between mounting block member 62 and support arm 46.The pressure exerted by the adjustable rod members on the peripheralsurface of the record band is controlled by means of the spring member78.

It is to be understood that the above-described arrangements areillustrative of the application of the principles of the invention.Other arrangements may be devised by those skilled in the art withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. In a sound recording and reproducing system a revolvable recordmember, a transducer unit disposed adjacent and adapted to ride on thesurface of said record member, said unit comprising a mounting member, arecording-reproducing element fixedly disposed in said mounting member,and means disposed in said mounting member for establishing a tangentialrelationship between said recording-reproducing element and the surfaceof said record member, said means including a first rod member disposedin such manner as to extend an adjustable distance beyond said mountingmember, ride on the surface of said record member and precede saidrecording-reproducing element in its travel on said record member, and asecond rod member disposed in such manner as to extend an adjustabledistance beyond said mounting member, ride on the surface of said recordmember and follow said recording-reproducing element in its travel onsaid record member each of said rod members comprising a rounded-offportion which rides on the record member and a threaded portion whichengages an internally threaded portion of said mounting member in suchmanner as to be longitudinally displaceable by rotation.

2. In a magnetic recording and reproducing system a remrd member havinga magnetizable surface, an electromagnetic transducer unit disposedadjacent and adapted to ride on the surface of said record member, saidunit comprising a mounting member, a magnetic recording-rcproducing coremember fixedly disposed in said mounting member, and means disposed insaid mounting member for establishing a tangential relationship betweensaid core member and the surface of said record member, said meansincluding a first rod member disposed in such manner as to extend anadjustable distance beyond said mounting member, ride on the surface ofsaid record member and precede said core member in its travel on saidrecord member, and a second rod member disposed in such manner as toextend an adjustable distance beyond said mounting member, ride on thesurface of said record member and follow said core member in its travelon said record member each of said rod members comprising a rounded-01fportion which rides on the record member and a threaded portion whichengages an internally threaded portion of said mounting member in suchmanner as to be longitudinally displaceable by rotation.

3. In a magnetic recording and reproducing system,

a record member having a magnetizable surface, a magneticrecording-reproducing unit disposed adjacent and adapted to ride on thesurface of said record member, said unit comprising a frame, a magnetichead mounted on said frame, said head including a core having convergingpole tips and a recording-reproducing gap therebetween, and meanssecured to said frame for simultaneously establishing a tangentialrelationship between said recording-reproducing gap and the surface ofsaid record member, and a predetermined spacing between said pole tipsand said record member, said means including an adjustable advance balldisposed in such manner as to precede said pole tips, and a followermember substantially identical with said advance ball disposed in suchmanner as to follow said pole tips said advance ball and follower membereach comprising a threaded portion which engages an internally threadedportion of said frame in such manner as to be longitudinallydisplaceable by rotation.

References Cited in the file of this patent UNITED STATES PATENTS934,843 Schaefer Sept. 21, 1909 2,361,752 Eilenberger Oct. 31, 19442,361,753 Eilenberger Oct. 31, 1944 2,589,035 Begun Mar. 11, 1952

